1. Field of the Invention
This invention generally relates to bicycle brake shoes for bicycle braking devices. More specifically, the present invention relates bicycle brake shoes that does not excessively wear the rim while maintaining good performance in wet conditions.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has also become a very popular competitive sport. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving their components. One particular component of bicycles that has been extensively redesigned over the past years is the operation of the brakes.
There are several types of bicycle braking devices, which are currently available on the market. Some of the most popular types of bicycle braking devices include rim brakes and caliper brakes. With respect to caliper brakes, there are mainly three types of caliper brakes: a side pull type, a center pull type and a cantilever type. In a side pull type of cantilever braking device, a pair of brake arms are pivotally connected together about a center mounting bolt which attaches to the frame of the bicycle. Each of the brake arms has a lever portion which is coupled to the brake wire such that when the rider operates the brake lever of the brake operating device, the lever portions of the brake arms are pulled together, which in turn moves the brake shoes attached to the other end of the brake arms together against the rim of the bicycle wheel. Return springs are provided for biasing the brake arm away from the bicycle wheel rim when the rider releases the brake lever. Side pull types of caliper braking devices are commonly used in road bikes.
A center pull type of caliper brake device operates similarly to the side pull type, except that the brake arms are attached to a brake arm bridge such that each brake arm is pivotally coupled at a separate pivot point on the brake arm bridge. The brake arm bridge is attached directly to the frame of the bicycle. A straddle cable interconnects the two lever portions of the brake arms such that a main brake wire, which is coupled to the straddle wire, pulls the lever portions of the brake arms together.
A cantilever type of braking device is generally mounted on bicycles designed for off-road use, such as mountain bikes (MTB) and all terrain bikes (ATB). In particular, a cantilever type brake device is designed to provide a powerful braking force. A cantilever type of brake device is equipped with a pair of brake arms, which are rotatably supported in a cantilever fashion on the front or rear fork of the bicycle frame, with the brake shoes attached midway between the ends of the brake arm. Typically, the lower portions of the brake arms are rotatably supported on the bicycle frame and the upper portions are linked to the brake cable or wire. The brake shoes are arranged opposite one another on either side of the bicycle wheel rims which is located between the brake arms. With this cantilever type of braking device, the bicycle arms rotate in a closing direction when the brake cable is pulled by the brake lever, which in turn results in the brake shoes being pressed against the rim to apply a braking force.
In each of these types of caliper braking devices, the brake shoe contacts side surfaces of the rim. It is important that the brake shoe provides good braking performance in both wet and dry conditions. Moreover, it is desirable that the brake shoe does not excessively wear the rim. Prior art bicycle brake shoes art typically molded from a rubber that is cross-linked with sulfur.
The braking surfaces of the bicycle rim can be hard and shiny surfaces that have been anodized, or the braking surface can be been ground and then polished to form a bicycle rim with softer braking surfaces. In the case of the anodized rim, the braking surfaces are hard and shiny which results in good braking performance in dry conditions, but poor braking performance in wet conditions. In the case of ground and polished braking surfaces, the conventional rubber brake shoes provide good braking performance in dry conditions, and better braking performance in wet conditions than hard and shiny braking surfaces with an anodized finish.
Attempts have been made to improve braking performance, especially in wet conditions, by manufacturing rubber brake shoes with refractory fillers. For example, rubber brake shoes have been manufactured with alumina (AL2O3). While such improved rubber brake shoes provide good wet and dry performance, such brake shoes with alumina cause too much wear of soft braking surfaces in the ground and polished types of rims. The trend in the bicycle industry is to produce more and more rims that have ground and polished braking surfaces. Since these braking surfaces are softer than the braking surfaces of the anodized rim, the alumina improved brake shoes should not be used because of the excessive amount of wear on these types of rims.
In view of the above, there exists a need for a bicycle brake shoe which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
One object of the present invention is to provide bicycle brake shoes that has improved braking performance in wet conditions.
Another object of the present invention is to provide bicycle brake shoes that does not excessively wear the rim during deceleration or stopping of the rim by the bicycle brake shoes braking while maintaining good performance in wet conditions.
The foregoing objects can be further attained by providing a bicycle brake shoe comprising a rim contacting portion with a braking surface formed from a non-sulfur cross-linked polymer that is cross-linked with zinc methacrylate.
The foregoing objects can be further attained by providing a bicycle brake shoe comprising a rim contacting portion with a braking surface formed from a polymer selected from the group consisting of butadiene rubber and acrylonitrile-butadiene rubber that is cross-linked with peroxide and a metal ion cross-linking.
The foregoing objects can also basically be attained by providing a bicycle brake shoe comprising a rim contacting portion with a braking surface formed from a polymer selected from the group consisting of butadiene rubber and acrylonitrile-butadiene rubber that cross-linked with zinc methacrylate. In the preferred embodiment, the rim contacting portion is further formed by cross-linking the butadiene rubber or the acrylonitrile-butadiene rubber with peroxide.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.